Ultrasound flow measurement method

ABSTRACT

The invention concerns a method and a device for ultrasound measurement of the flow of flowing media with a measuring tube (1), with at least two pairs of ultrasound transducers arranged on the measuring tube, each forming a measuring path (M1,M2,M3,M4,M5), with a transducer (2) determining the velocities of the medium along the measuring paths (M1,M2,M3,M4,M5) from the signals of the pair of ultrasound transducers and with an adder (3) determining the flow quantity of the medium from the velocities of the medium along the measuring paths (M1,M2,M3,M4,M5). 
     According to the invention, such a method and such a device are designed with a Reynolds&#39; number meter (5) that determines the Reynolds&#39; number constantly and a flow-quantity corrector (6) connected to the adder (3) and the Reynolds&#39; meter (5).

According to a first theory, the invention concerns an ultrasound methodof measuring the flow of flowing media using a measuring tube and atleast two pairs of ultrasound transducers attached to the measuring tubeforming a measuring path, in which the amount of flowing medium isdetermined from the velocity of the medium along at least two measuringpaths. The term medium here includes both liquids and gases.

According to a second theory, the invention also concerns a device forusing the ultrasound method of measuring the flow of flowing media witha measuring tube, at least two pairs of ultrasound transducers arrangedon the measuring tube forming a measuring path, a transducer determiningthe velocities of the medium along the measuring path from the signalsof the pair of ultrasound transducers and an adder that finds the amountof flowing medium from the velocity of the medium along the measuringpaths.

The known methods and devices for measuring the average velocity and theamount of flow of a flowing medium by ultrasound use a large number ofmeasuring paths, which form the supporting points of a digitalintegration method that is as optimal as possible Here, the integrationmethod is normally determined by the dimension or geometry of themeasuring path and the measuring tube. There are various traditionaloptimal integration methods by Chebichev, Gauss or Taylor, which aregiven for example in unexamined patent applications CH-A-610 038,DE-A-30 38 213 and EP-A-0 125 845. The methods and devices known fromthese unexamined patent applications are dependent on the viscosity ofthe medium and hence on the Reynolds' number for their precision. Forexample, please refer to the article "A New Integration Technique forFlowmeters with Chordal Paths" in Flow Measurement and Instrumentation,vol. 1, No. 4, July 1990, Pages 216 to 224.

The methods and devices known from said unexamined patent applicationsfor ultrasound flow measurement have insufficient precision due to theirdependence on the viscosity of the medium, since the viscosity canchange sharply during measurement, particularly as a result oftemperature changes. However, high precision is generlly requiredparticularly when measuring quantities of flowing gases, petroleumproducts and chemical products, for example second important problemwith the known methods and devices is disturbances in the velocityprofile caused by integration effects, which also has a negativeinfluence on precision.

The products specified have extraordinarily high requirements formeasurement precision. For example, for petroleum, in the range of aflow quantity from 50% to 100% of the nominal flow quantity, the maximumerror is ±0.15%, and in the range of a flow quantity 10% to 100% of thenominal flow quantity, the maximum error is ±0.25%. In the past, thisprecision could only be guaranteed with turbine meters.

When measuring the quantity of a medium flowing in a measuring tube, itis advantageous not to disturb the flow of the medium. At the same time,the point is to obtain the high measurement precision required using arelatively inexpensive device, which also has a long life it is alsoadvantageous if such a device can be calibrated with water afterproduction and can then be recalibrated with other liquids or even gasesduring operation by the users, in order to guarantee the precisionrequired.

The task of the invention is therefore to eliminate the problemsmentioned and to provide a method and a device with which such highprecision can be guaranteed. Another task of the invention consists ofmaking it possible with the method and device in the invention tosharply reduce the influence of the viscosity of the medium. The task ofthe invention is also to provide a method and a device that reduce theinfluence of changes in the flow profile and that offer the possibilityof self-calibration during operation. Finally, it is also the task ofthis invention to provide a method and a device that make possibleconstant determination of viscosity of the medium, hence in "real-time,"and that also make it possible to identify the type of medium, forexample, the type of flowing petroleum, based on the viscosity and thesound velocity and/or sound dissipation. According to the invention, thetasks listed and inferred above in the first theory are solved with anultrasound method of measuring the flow of flowing media where theReynolds' number of the flowing medium is constantly measured and wherethe value for the flow quantity is corrected using the value for theReynolds, number In one advantageous design, the Reynolds' number isdetermined using the velocity of the medium along at least two measuringpaths. These velocities of the flowing medium on various measuring pathscan be determined simultaneously or in sequence.

In the second theory of the invention, the tasks listed and inferredabove are solved with a device for using the ultrasound method ofmeasuring the flow of flowing media, characterized by the fact that ithas a Reynolds' number meter that constantly determines the Reynolds'number and a flow-quantity corrector connected to the adder and theReynolds' number meter.

One especially preferred design of this invention provides that beforethe Reynolds' number is determined during operation, an operating flowprofile based on the velocity measured is recorded and in the event thatthe current flow profile is disturbed by inlet effects or other causes,an arithmetic correction of it is made based on a predeterminedundisturbed calibration flow profile.

Now there are many ways of designing and improving the ultrasound methodof measuring flowing media in the invention and the device for using theultrasound method of measuring flowing media in the invention. For this,please refer on one hand to the patent claims subordinate to Patentclaims 1 to 25, and on the other hand to the description of preferredexamples of embodiment in connection with the drawings.

FIG. 1 shows a block diagram of a first example of embodiment of adevice according to the invention for using an ultrasound method ofmeasuring flowing media,

FIGS. 2 a)-f) shows a flow diagram with explanations of the processes inthe correction of the flow profile,

FIGS. 3 a),b) shows a graphic example of a correction in flow profileswith high Reynolds' numbers and low Reynolds' numbers,

FIGS. 4 a),b) shows graphs of the improvement in precision when themethod in the invention is used for media with different viscosities,

FIG. 5 shows a block diagram of a second example of embodiment of thedevice in the invention for using an ultrasound method of measuringflowing media,

FIG. 6 shows a block diagram of an example of embodiment for aflow-profile corrector,

FIG. 7 shows a block diagram of an example of embodiment for a Reynolds'number meter,

FIG. 8 shows an example of an error curve based on empirical data foruse in a flow corrector according to the invention and

FIGS. 9 a)-d) shows the dependence of various velocity ratios on theReynolds' number to explain the function of the method and the device inthe invention.

With the device used for the ultrasound measurement method in theinvention, at least two, but advantageously five velocities are measuredon different measuring paths; the measuring paths are formed by pairs ofultrasound transducers consisting of ultrasound transducers assigned toone another and arranged on different sides of the measuring tubePreferably, a flow profile of the medium in a line connected to thedevice in the invention has been made using inlet and outlet sectionsand developed as fully as possible. The calibration flow profilementioned is preferably the best possible approximation of the flowprofile in a fully developed flow. It is known from practice that thevelocities on certain measuring paths are less dependent on theReynolds' number and on other measuring paths more dependent on it. Themeasuring paths less dependent on the Reynolds' number are those at adistance of one half the radius of the measuring tube to the wall of themeasuring tube. On the other hand, the measuring paths more dependent onthe Reynolds' number are, for example, in the middle or near the wallsof the measuring tubes. With the latter measuring paths, the flowprofile has a maximum influence on the Reynolds' number. The device inthe invention can also work with more or less than five measuring paths,but there must be at least one measuring path among them that isrelatively less dependent on the Reynolds' number.

Since the Reynolds' number in the device in the invention is measuredconstantly, this measurement can be used in real time to correct theamount of flow and potentially to determine the viscosity and, ifnecessary, also to identify the medium. This will be explained below.

Preferably, the velocities of the flowing medium measured on themeasuring paths are used to determine the Reynolds' number. However, itis also possible to determine the Reynolds' number in other ways, forexample based on measurement of the ultrasound damping The value for theReynolds' number found is then used to make a correction in the flowquantity using a error curve. Of course, a value for the volume can alsobe determined from the average velocity and the flow quantity.

The method and the device for using it will now be explained withreference to FIG. 1. Five pairs of ultrasound transducers connected tomeasuring tube 1 and forming measuring paths M1 to M5 are connected to atransducer 2, which determines the various velocities of the flowingmedium along measuring paths M1 to M5, for example from the running-timedifferences in the ultrasound signals. These velocities are fed to anadder 3 via various units explained later, where they are multiplied bycorresponding weight factors and then totaled. The average velocityclose to the output of the adder 3, hence the flow quantity for thesurface area of the cross section of the measuring tube, is close to aflow corrector 6 for correcting the flow quantity. An error curve shownfor example in FIG. 8 based on empirical data is stored in the flowcorrector 6, and besides the Reynolds' number, it contains all othertechnological tolerances connected with the device in the invention.These tolerances are carefully measured after production of the devicein the invention that uses the ultrasound method of flow measurement inthe invention. The flow quantity calculated by the transducer 2 is nowcorrected based on a Reynolds' number determined by a Reynolds' numbermeter 5. The corrected flow quantity given by the flow corrector 6 isthen shown by an optional indicator device 4. As already mentioned, thedevice in the invention can be calibrated with water, and themeasurement results obtained during calibration can also be transferredto other media, like other liquids and even gases, since the followingapplies to the Reynolds' number Re: ##EQU1## where V_(w) and V_(m) arethe flow velocities of water and a second medium. V_(w) and V_(m) arethe kinematic viscosities of water and the medium, while D is thediameter of the measuring tube 1. At 20° C., the following applies:

    V.sub.water =10.sup.-6 m.sup.2 /s

and

    V.sub.air =15·10.sup.-6 m.sup.2 /s

This means that a device calibrated with water using the ultrasoundmethod of measuring the flow in the invention works with the medium air,if the velocity of the air is higher by a factor of 15 than the velocityof the water during calibration.

Before determining the Reynolds' number, it is important to check thesymmetry of the flow profile using the velocity ratios or velocitydifferences. If the actual flow profile is not disturbed or fullydeveloped, the measured velocities will be used for further processing.A high symmetry of the flow profile is promoted, for example by puttinga Venturi nozzle in the line.

Before the device in the invention is started up by the user, it iscalibrated, with water for example. Calibration is done in the range inwhich the device will later be used, for example in a range for theaverage velocity of 0.1 m/s to 6 m/s, for a large number of measuringpoints, for example for 10%, 20%, 50% and 100% of the maximal averagevelocity. During this calibration, the velocities of the flowing mediummeasured for each measuring path are filed in a storage device when thecalibration flow profile is not disturbed. This so-calledcalibration-profile matrix is characteristic for the device using theultrasound method of flow measurement in the invention, since thismatrix contains all of the mechanical, electronic, acoustic andhydraulic tolerances.

When correcting the symmetry of the current flow profile, two cases thatdepend on the Reynolds' number must be differentiated. On one hand, thecase where one is working with large Reynolds' numbers above roughly100,000 and, on the other hand, the case where one is working withsmaller Reynolds' numbers. In the first case, the calibration-profilematrix for five measuring paths //EPM// takes the following form:##EQU2## V1p, . . . V5p are the velocities of the flowing medium alongthe corresponding measuring paths during the calibration flow profile,

ΣVp is the corresponding average velocity or flow quantity per measuringtube cross section at the calibration flow profile,

G1, . . . G5 are the weight factors assigned to the measuring paths, and10%, . . . 100% are the measuring points in the operating range.

With the device using the method in the invention mounted and ready foroperation, first the operating profile matrix //BPM// is recorded inanother Calibration process, and takes the following form: ##EQU3##where V1b . . . V5b re the velocities along the corresponding measuringpaths with the operating flow profile,

ΣVb is the corresponding average speed or flow quantity per measuringtube cross section at the operating flow profile, and

G1, . . . G5 are in turn the weight factors of the measuring paths,

For the operating profile matrix //BPM// just introduced, the flowquantities in the measuring tube in a uniformity range, hence forReynolds' numbers greater than 100,000, identical to the flow quantitieswhen the calibration flow profile is recorded, are set artificially--forexample using a mobile, calibrated flow-quantity generator. In thiscase, the following is true:

    ΣVb.sub.100% =ΣVp.sub.100%                     (Equation 3)

However, in practice, it is difficult to make Equation 3 come outprecisely enough, since frequently the same flow quantities cannot beset exactly. To be able to correct the flow profile, Equation 3 is putin the following form:

    β·ΣVb.sub.100% =ΣVp.sub.100%     (Equation 3a)

In Equation 3a, β is an interpolation factor to correct the fact thatthe same flow quantities cannot generally be set. Equation 3a isidentical to

    β. . . V5b.sub.100% ·G5·β∥=∥ΣV.sub.P.sbsb.100% ∥                                                (Equation 4)

Now a profile determinant //Pr Det// is introduced, for which thefollowing is true: ##EQU4## where //Dp_(100%) is the calibration profilematrix, and

//Db_(100%) is the profile determinant of the operating profile matrix.

When the method in the invention is used during operation by the user,the correction is made with the current profile matrix//APM//=//BPM//·//PrDef//: ##EQU5## where Σ vbgec are the correspondingcorrected average velocities or, flow quantities per cross sectionsurface of the measuring tube in the measuring tube with the currentflow profile.

In the form shown, Equation 6 applies only to media that behave linearlyover the range considered from 10% to 100% of the nominal flow quantity.For nonlinear media, the corrections in the velocities of the mediumalong the measuring paths are made using the accompanying coefficientsfrom the calibration profile matrix and the operating profile matrix,for example V1p50%/V1b50% for a velocity of the flowing medium onmeasuring path M1 of V1b50%. In the case of nonlinear media, it is alsonecessary to introduce the coefficients β1, β2 . . . β5, see alsoEquation 3a. For nonlinear media, the correction coefficients are alsointerpolated between values known only discretely. After correction ofthe current flow profile using the calibration profile matrix and theoperating profile matrix, the relative error in the average velocitiesand flow quantities can be calculated with the following equation:##EQU6##

In summary, the profile matrices mentioned were used for processing asfollows. First, using calibration, the velocities of the medium on themeasuring paths and the accompanying average velocities and flowquantities were measured with an undisturbed calibration flow profileand then with an operating flow profile. Then the ratio between theaverage velocities and flow quantities when the calibration flowprofiles was recorded and the operating flow profiles was found. Afterthat, the current measured velocities of the medium along the measuringpaths with the current flow profile are changed in accordance with thatratio. Then, the ratios of the velocities of the medium along themeasuring paths with the calibration flow profile and the deviatingvelocities of the medium along the measuring paths with the operatingflow profile are found, and the corresponding velocities of the mediumalong the measuring paths with the current flow profile are multipliedby those ratios. Of course, if necessary, this correction is made withan interpolation.

After the flow profile above is corrected, if the velocity isundisturbed, the Reynolds' number can be determined based on that flowprofile.

As already mentioned, the correction in the flow profile that wasmentioned is made as a correlation of the Reynolds' number. Thecalibration profile matrix given in Equation 1 can only be used forlarge Reynolds' numbers, roughly larger than 100,000, because in thatcase the right side of the Navier-Stokes hydrodynamic base vectorequation disappears ##EQU7## where Ω is the rotation of the velocity V,which means that Ω=V·V and

Re is the Reynolds' number.

(See also Equation 41.23) in "The Feynman Lectures on Physics, Reading"by R. Feynman, R. Leighton, M. Sands, Massachusetts, Palo Alto, London,Addison-Wesley Publishing Company, Inc. 1964).

If the Reynolds' numbers age large, from the hydrodynamic equation 8,the hydrostatic base vector equation follows: ##EQU8##

For this case, the properties of the medium, for example, the viscosity,were left out of consideration, since their influence is small. Thissmall influence has as its result that the form of the flow profile inthe uniformity range for Reynolds' numbers over 100,000 only changesinsignificantly.

For the second case of smaller Reynolds' numbers, the influence of theproperties of the medium is positively essential, so that it isnecessary to use the calibration profile matrix in another form. Duringcalibration, in this case, the viscosity of the medium (v) and thediameter (D) of the measuring tube are measured, so that for eachcalibration flow profile, a corresponding Reynolds' profile matrix//EPM-Re_(p) // in dimensionless form is obtained: ##EQU9##

It can be inferred from Equation 10 that with the calibration done atthe start for each Reynolds' number, a calibration profile for thedevice for using the ultrasound method of flow measurement in theinvention can be stored in dimensionless form with compensation fortolerances (see FIG. 2a). Dimensionless means that the currentvelocities measured V1, . . . V5 are divided by the average velocity,hence the flow quantity per cross section surface area of the measuringtube at maximum flow quantity during calibration in the installed stateof the device in the invention, so that Vkii=Vi/Σ VK_(max).

When calibration is in the installed state, according to Equation 2, andthe operating flow profile deviates from the calibration flow profile,the velocities on the measuring paths and the average velocity, hencethe flow quantity per cross sectional surface of the measuring tube, aredetermined as follows:

    V1k.sub.max·G.sub.1. . . V5k.sub.max ·G.sub.5 ∥=∥ΣVk.sub.max ∥         (Equation 11)

From this follows lastly the dimensionless operating profile matrix,which looks like this: ##EQU10##

The dimensionless operating profile matrix is given in FIG. 2b.

Based on velocities V1k, . . . V5k of the flowing medium measured duringoperation on measuring paths M1 to M5, the Reynolds' number isdetermined in zero approximation Re₀ using equations not yet explainedFor this Reynolds' number in zero approximation Re₀, using equation 10for an identical Reynolds' number of the calibration Re_(p), thevelocities on the measuring paths, which can be shown in analytic formas functions, are determined from the calibration flow profiles (seeFIG. 2c). From these velocities on the measuring paths, the averagevelocity Vpgem is determined at the same time. This profile is thencompared with the current flow profile (see FIG. 2d), in which theaverage velocity found Vgemn (in zero approximation n=0, hence Vgem0) iscompared with the average velocity Vpgem of the calibration flow profile(dVgem=Vgemn-Vpgem). If the difference between the average velocities isgreater than a certain maximum value ε, then in a subsequent iterationprocess a smaller difference is assumed, for example Vgem(n+1)=Vgemn+dvgem/2. From the new Average velocity, the Reynolds' numberRe₁ of the first approximation from the equation Re₁ =Vgem1·D/v isdetermined. Using this Reynolds' number in first approximation, from thestored calibration profile matrix, a new average velocity is found,which is then in tern compared (see FIGS. 2e and 2f). If the differencefound dVgem is smaller than the maximum value given ε, the last valuefound for the Reynolds' number is used to correct the flow quantity.Improved precision is guaranteed using the iteration process described.

FIGS. 3a and 3b show examples of corrected dimensionless flow profilesfor large Reynolds' numbers (FIG. 3a) and small Reynolds' numbers (FIG.3b). In both figures, a is for the calibration flow profile, b thedisturbed operating flow profile and c the corrected operating flowprofile.

After the correction of the flow profile described, the last value foundfor the Reynolds' number is forwarded to the flow corrector 6 to correctthe flow quantity. The whole method takes place in real time.

FIGS. 4a and 4b show graphs of the increased precision with theinvention. FIG. 4a shows, for an example of embodiment with fivemeasurement paths, the percentage of errors with three media withdifferent viscosities (20 cSt, 40 cST and 50 cSt) as a correlation ofthe velocity in m/s with a state-of-the-art method (see curves a, b andc) and with the device in the invention using an ultrasound method ofmeasuring the flow of flowing media (see curves d, e and f). Here it isclear that the percentage of error in values, for the most part over0.5% with the state-of-the-art methods, is reduced by the method in theinvention to values under 0.2% for all three media.

FIG. 4b shows, for the same three media with different viscosities, thepercentage of errors for the same measurement results that are shown inFIG. 4e, but now not as a function of the velocity, but as a function ofthe Reynolds' number, in turn before and after correction. Here, what isstriking is that all three curves a, b and c basically coincide whenshown as a function of the Reynolds' number. Here again, it is clearthat the precision is decisively improved with the ultrasoundflow-measurement method in the invention.

Depending on whether the flow profile has a turbulent or a laminarcharacter, the Reynolds' number is determined as follows:

For a flow profile with a turbulent character, the Reynolds' number isfound from the velocity ratios or differences in measuring paths 2 and 4(V₂ +V₄) and measuring paths 1 and 5 (V₁ +V₅).

For a flow profile with laminar character, the Reynolds' number is foundfrom the velocity ratios or differences in the velocities on measuringpaths 2 and 4 (V₂ +V₄) and measuring path 3 (V₃).

The Reynolds' number can thus be found based on velocity ratios (case a)for the velocities on the measuring paths and also based on velocitydifferences (case b) for the velocities on the measuring paths both forflow profiles with turbulent characters and for flow profiles withlaminar characters.

For case a, where the Reynolds' number is found based on the velocityratios, there is a flow profile with laminar character under thefollowing condition:

    (V.sub.2 +V.sub.1)/V.sub.3 <1.9                            (Equation 13)

Inversely, a flow profile has a turbulent character when the followingapplics:

    (V.sub.2 +V.sub.4)/V.sub.3 <1.9                            (Equation 14)

The following equations for determining the Reynolds' number were foundempirically.

For a flow profile with laminar character, the following applies to theReynolds' number.

    Re.sub.1 =19100((V.sub.2 +V.sub.4)/V.sub.3).sup.2 -60200(V.sub.2 +V.sub.4)/V.sub.3 +47700                                  (Equation 15)

In contrast, for a flow profile with a turbulent character, for theReynolds' number, if it is smaller than 30,000, the following applies

    Re.sub.1 =6500+39000√(5.14(V.sub.2 +V.sub.4)/(V.sub.1 +V.sub.5)-5,22)(Equation 16)

For a Reynolds' number >20,000, with a flow profile with a turbulentcharacter, the following is true.

    Re.sub.1 =5080000((V.sub.2 +V.sub.4)/(V.sub.1 +V.sub.5)).sub.2 -108600000(V.sub.2 +V.sub.4)/V.sub.1 +V.sub.5)+5833000    (Equation 17)

For case b, in which the Reynolds' number is determined based onvelocity diffe4onces, the flow profile has a laminar character, if thefollowing is true:

    (V.sub.2 +V.sub.4)-1.9V.sub.3 <0                           (Equation 18)

Inversely, there is a flow profile with a turbulent character if:

    (V.sub.2 +V.sub.4)-1.9V.sub.3 >0                           (Equation 19)

If the flow profile has a laminar character, the following now applies:

    Re.sub.1 =A.sub.1 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5)/2).sup.2 +B.sub.1 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5))/2+C.sub.1         (Equation 20)

In contrast, the following is true of a flow profile with a turbulentcharacter for Reynolds' numbers smaller than 30,000:

    Re.sub.1 =A.sub.2 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5)/2).sup.2 +B.sub.2 ((V.sub.3 +V.sub.4)-(V.sub.1 +V.sub.5))/2+C.sub.2         (Equation 21)

Finally, for Reyolds' numbers greater than 20,000 and flow profiles withturbulent character, the following is true:

    Re.sub.1 =A.sub.3 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5)/2).sup.2 +B.sub.3 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5))/2+C.sub.3         (Equation 22)

The coefficients A₁ to A₃, B₁ to B₃ and C₁ to C₃ in Equations 20 to 22are found empirically.

As already described, for the purpose of smooth functioning of the flowcorrector during operation by the user, the current flow profile iscontrolled for deviations from the calibration flow profiles orasymmetries. This control is done using a profile meter 7 and a profilecorrector 9, connected between the transducer 2 and the adder 3. Theyare explained below with reference to FIGS. 5 and 6. The profile meter 7compares the velocities on the measuring paths and if there are profiledeviations or a defective sensor, it gives a special signal from itsoutput 23 to the profile corrector 9 and to an alarm 8. Now, duringinstallation, due to installation or inlet effects like curvatures andcomparable disturbances, if a disturbed flow profile occurs, thedeviation in this disturbed flow profile from the calibration flowprofiles or the asymmetries in the disturbed flow profile can basicallybe eliminated by the profile corrector 9. This profile corrector 9 workson the basis of Equations 1 to 12. A switch 22 shown in FIG. 6, forminga unit inside the profile corrector 9, has three settings: setting a forflow profile calibration, setting b for flow profile adjustment andsetting c for flow profile monitoring.

Switch 11 is in setting a if the device in the invention using anultrasound method of measuring the flow of flowing media is calibratedwith an undisturbed reference flow profile. In this setting, thecalibration profile matrix //EPM// is stored in the calibration flowprofile memory 12 (see also Equation 1).

If the device in the invention using the ultrasound method of measuringthe flow of flowing media is installed by the user, the flow Entity inthe like connected to the device in the invention is basically set atthe maximum possible flow quantity during operation. In this case,switch 11 is in setting be In this setting, the operation profile matrix//BPM// is stored in an operating profile memory 13 (see also Equation2) Next a profile compare 14 determines the profile determinants//PrDet// based on Equations 3, 4 and 5.

Under normal conditions, switch 11 is in setting C during operation, sothat the information on the velocities on the measuring paths isforwarded from the switch 11 directly to a profile transducer 15, whichworks according to Equation 6. At the output of the profile transducer15, in principle, an undisturbed and corrected flow profile isavailable. Based on this flow profile, the Reynolds' number isdetermined in the Reynolds' number meter 5. which is then made availableto the flow corrector 6. This flow corrector 6 works with an error curvethat also takes into account technological tolerances of the device.FIG. 8 shows an example of such an error curve, wherein a maximum errorof 0.15% is guaranteed by using this error curve.

If there are changes in the line connecting to the measuring tube orother hydraulic transitional processes, for example, if a control valvecloses, the flow profile changes very quickly. This change is controlledby the profile meter 7, and if the change is significant, it gives asignal via output 23 to the alarm 8 and the profile corrector 9 (seealso FIG. 6). In the profile corrector 9, the switch 11 is then switchedfrom setting c to setting b. In this setting, the operating flow profileprovided by the operating profile memory 13 is compared with thecalibration flow profile from the calibration flow profile memory 12. Ifthere is too great a deviation between these two flow profiles, afeedback signal is given to switch 11 via the feedback output 22,whereupon an operating flow profile is filed again in the operating flowprofile memory 13. This happens until there is a corrected operatingflow profile in real time, which is then fed back to the transducer 15by switch 11 in setting c.

The values for the velocities at the output of the profile meter 7 arefed to the Reynolds' number meter 5 as well as to the adder 3 (see alsoFIGS. 7 and 8). A turbulent laminar switch 16 in this Reynolds' numbermeter 5 works based on equations 13 and 14 or 18 and 19. This turbulentlaminar switch 16 is connected to a laminar flow meter 17, a turbulentflow meter 18 and a transitional flow meter 19, wherein these flowmeters 17, 18 and 19 work based on Eqations 15, 16 and 17 or 20, 21 and22. The values at the outputs of these flow meters 17, 18 and 19 for theReynolds' number are then fed to an operations output amplifier 20.

In FIGS. 9a to 9d, the ratios on which the function of the Reynolds'number meter 5 is based are shown graphically as an example. FIG. 9ashows a graph of the ratio (V₂ +V₄ /V₃) as a function of the Reynolds'number, which is traced in millions, whose course the action of theturbulent laminar switch 16 affects. FIG. 9b shows a graph of theReynolds' number as a function of the ratio (V₂ V₄ /V₃) whose curve theaction of the laminar flow meter 17 affects. FIG. 9b shows bothexperimentally determined measurement data and theoretical data. FIGS.9c and 9d show the dependence of the Reynolds' number, which is tracedin increments of a thousand, on the ratio (V₂ +V₄ /(V₁ +V₅), whose curvethe processing in the turbulent flow meter 18 affects. FIGS. 9c and 9dshow the connections mentioned both for measurement data, with oil andwater as the flowing media, and also for theoretically determined data.For 9c, it is true to some extent that the Reynolds' number is smallerthan 30,000, while for FIG. 9d it is true that the Reynolds' number issomewhat larger than 20,000.

The value determined in real time at the output of the operation outputamplifier 20 for the Reynolds' number is fed to a viscosity meter 10 aswell as to the flow corrector 6. This viscosity meter 10 determines theviscosity of the medium, based on the Reynolds' number, the averagevelocity, hence the flow quantity per cross sectional surface area ofthe measuring tube and the diameter of the measuring tube 1.

The viscosity value at the output of the viscosity meter 10 is sent onfirst to a display device 4 and then to a medium identifier 24. Thismedium identifier 24 also provides the ultrasound velocity determined bythe transducer 2 within the medium and/or the ultrasound damping of themedium. Based on the viscosity of the medium, the ultrasound velocity inthe medium and/or the ultrasound damping of the medium, the mediumidentifier 24 determines the type of medium, for ale, the type ofpetroleum, by making a comparison with data stored for down media.

We claim:
 1. An ultrasound method of measuring the flow of a flowingmedium, using a measuring tube and at least two pairs of ultrasoundtransducers arranged on the measuring tube forming a measuring path, inwhich the rate of flow of the flowing medium is determined from thevelocities of the medium along at least two measuring paths, wherein theReynolds' number of the flowing medium is measured continuously and thevalue for the rate of flow is corrected using the value for theReynolds' number, wherein the Reynolds' number is determined using thevelocities of the medium along at least two measuring paths.
 2. Themethod according to claim 1, characterized by the fact that the rate offlow is corrected using the value for the Reynolds' number and an errorcurve based on empirical data.
 3. The method according to claim 1,characterized by the fact that the Reynolds' number is determined usingan arithmetical algorithm from the velocities of the medium alongdifferent measuring paths.
 4. The method according to claim 3,characterized by the fact that the Reynolds' number is determined basedon ratios of said velocities along different measuring paths.
 5. Themethod according to claim 3, characterized by the fact that theReynolds' number is determined based on subtractions of the velocitiesalong different measuring paths.
 6. An ultrasound method of measuringthe rate of flow of a flowing medium, using a measuring tube and atleast two pairs of ultrasound transducers arranged on the measuring tubeforming a measuring path, in which the rate of flow of the flowingmedium is determined from the velocities of the medium along at leasttwo measuring paths, wherein the Reynolds' number of the flowing mediumis measured continuously and the value for the rate of flow is correctedusing the value for the Reynolds' number, wherein the velocities of theflowing medium V1, V2, V3, V4 and V5 are determined along five differentmeasuring paths 1 to 5, and wherein a turbulent flow for (V2+V4)/V3>1.9and a laminar flow for (V2+V4)/V3<1.9 is assumed.
 7. The methodaccording to claim 6, wherein the case of a turbulent flow, theReynolds' number is determined from the velocity ratios or differencesin the sum of the velocities along measuring paths 2 and 4 (V2+V4) andthe measuring paths 1 and 5 (V2+V5), and wherein in the case of alaminar flow it is determined from the velocity ratios or differences inthe sum of the velocities along measuring paths 2 and 4 (V2+V4) andmeasuring path 3 (V3).
 8. The method according to claim 7, wherein for alaminar flow, the Reynolds' number is determined from the velocityratios as follows:

    Re.sub.1 =19100((V.sub.2 +V.sub.4)/V.sub.3).sup.2 -60200(V.sub.2 +V.sub.4)/V.sub.3 +47700.


9. The method according to claim 8, wherein for a turbulent flow, theReynolds' number is determined as follows from the velocity ratios:

    Re.sub.t <30000Re.sub.t =6500+39000((5,14(V.sub.2 +V.sub.4)/V.sub.1 +V.sub.5)-5,22).sup.1/2 Re.sub.t =5080000((V.sub.2 +V.sub.4)/(V.sub.1 +V.sub.5)).sup.2

    Re.sub.t >20000-108600000(V.sub.2 +V.sub.4)/(V.sub.1 +V.sub.5)+5833000.


10. The method according to claim 8, wherein for laminar flow, theReynolds' number is determined from the velocity difference as follows:

    Re.sub.1 =A.sub.1 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5)/2).sup.2 +B.sub.1 ((V.sub.2 +V.sub.4)-V.sub.1 +V.sub.5))/2+C.sub.1

where A₁, B₁, and C₁ are determined empirically.
 11. The methodaccording to claim 8, wherein for a turbulent flow, the Reynolds' numberis determined as follows from the velocity differences:

    Re.sub.t <30000Re.sub.t =A.sub.2 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5)/2).sup.2 +B.sub.2 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5))/2+C.sub.2

    Re.sub.t <20000R.sub.t =A.sub.3 ((V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5)/2).sup.2 +B.sub.3 (V.sub.2 +V.sub.4)-(V.sub.1 +V.sub.5))/2+C.sub.3,

where A₂, B₂, C₂, A₃, B₃ and C₃ are determined empirically.
 12. Themethod according to claim 6, wherein in a calibration process,calibration flow profiles that are as undisturbed as possible arerecorded from the velocities of the medium along the measuring paths forvarious rates of flow and Reynolds' numbers.
 13. The method according toclaim 12, wherein in a calibration process, at least one operating flowprofile is recorded with the help of a device mounted and ready tooperate that uses the method according to anyone of claims 6 to
 12. 14.The method according to claim 13, wherein deviations between thecalibration flow profiles and the operating flow profiles are correctedarithmetically.
 15. The method according to claim 14, wherein forReynolds' numbers greater than 100,000, to record the operating flowprofile, rates of flow for the medium are set that correspond as much aspossible to the rates of flow when the calibration flow profile isrecorded, wherein the ratios between the individual velocities along themeasuring paths of the calibration flow profile and the operating flowprofile are determined, wherein with these ratios, the current measuredvelocities along the measuring paths are corrected, and wherein thatwith this correction, the measured velocities are also corrected withthe ratios of the rates of flow when the calibration flow profiles arerecorded and when the reference flow profiles are recorded.
 16. Themethod according to claim 15, wherein the correction factors between therates of flow set during the recording of the calibration flow profileand the operating flow profile are determined using interpolation. 17.The method according to claim 14, wherein especially for Reynolds'numbers smaller than 100,000, the calibration profiles are measured andstored in dimensionless form for a large number of Reynolds' numbers,wherein the current measured velocities and the current rate of flow fora dimensionless current flow profile are processed, and wherein thedimensionless current flow profile is compared with the calibration flowprofiles and corrected by using said comparison.
 18. The methodaccording to claim 17, wherein:the Reynolds' number in zeroapproximation is determined from the current flow profile; the averagevelocity is determined from the flow profile stored for the Reynolds'number in zero approximation; the average velocity from the memory iscompared with the current average velocity, if there is a deviationbetween the average velocities above a predetermined limit, a newcurrent average velocity is assumed that deviates less from the averagevelocity from the memory; the Reynolds' number is determined in firstapproximation from the new currently determined velocity; the averagevelocity is determined again from the flow profile stored with theReynolds' number in first approximation; if there is a new deviationabove the predetermined limit, a new current average velocity is againtaken that deviates less from the average velocity from the memory; andotherwise, the last value for the Reynolds' number is used for furtherprocessing.
 19. The method according to claim 6, wherein the viscosityof the medium is determined using the rate of flow, the diameter of themeasuring tube and the Reynolds' number.
 20. The method according toclaim 19, wherein the medium is identified using the viscosity andparticularly other medium-dependent measured variables.
 21. The methodaccording to claim 20, wherein the ultrasound velocity and/or theultrasound damping of the medium are determined as anothermedium-dependent measured variable.
 22. The method according to claim 6,wherein the rate of flow is corrected using the value for the Reynolds'number and an error curve based on empirical data.
 23. The methodaccording to claim 6, wherein the Reynolds' number is determined usingthe velocities of the medium along at least two measuring paths.
 24. Themethod according to claim 23, wherein the Reynolds' number is determinedusing an arithmetical algorithm from the velocities of the medium alongdifferent measuring paths.
 25. The method according to claim 24, whereinthe Reynolds' number is determined based on ratios of said velocitiesalong different measuring paths.
 26. The method according to claim 24,wherein the Reynolds' number is determined based on subtractions of thevelocities along different measuring paths.
 27. An ultrasound method ofmeasuring the rate of flow of a flowing medium, using a measuring tubeand at least two pairs of ultrasound transducers arranged on themeasuring tube forming a measuring path, in which the rate of flow ofthe flowing medium is determined from the velocities of the medium alongat least two measuring paths, wherein the Reynolds' number of theflowing medium is measured continuously and the value for the rate offlow is corrected using the value for the Reynolds' number wherein in acalibration process, calibration flow profiles that are undisturbed aspossible are recorded from the velocities of the medium along themeasuring paths for various rates of flow and Reynolds' numbers.
 28. Themethod according to claim 27, wherein the viscosity of the medium isdetermined using the rate of flow, the diameter of the measuring tubeand the Reynolds' number.
 29. The method according to claim 28, whereinthe medium is identified using the viscosity and particularly othermedium-dependent measured variables.
 30. The method according to claim29, wherein the ultrasound velocity and/or the ultrasound damping of themedium are determined as another medium dependent measured variable. 31.The method according to claim 27, wherein the rate of flow is correctedusing the value for the Reynolds' number and an error curve based onempirical data.
 32. The method according to claim 27, wherein theReynolds' number is determined using the velocities of the medium alongat least two measuring paths.
 33. The method according to claim 32,wherein the Reynolds' number is determined using an arithmeticalalgorithm from the velocities of the medium along different measuringpaths.
 34. The method according to claim 33, wherein the Reynolds'number is determined based on ratios of said velocities along differentmeasuring paths.
 35. The method according to claim 33, wherein theReynolds' number is determined based on subtractions of the velocitiesalong different measuring paths.
 36. The method according to claim 27,wherein in a calibration process, at least one operating flow profile isrecorded with the help of a device mounted and ready to operate thatuses the method according to any one of claims 27 to
 35. 37. The methodaccording to claim 36, wherein deviations between the calibration flowprofiles and the operating flow profiles are corrected arithmetically.38. The method according to claim 37, wherein for Reynolds' numbersgreater than 100,000, to record the operating flow profile, rates offlow for the medium are set that correspond as much as possible to therates of flow when the calibration flow profile is recorded, wherein theratios between the individual velocities along the measuring paths ofthe calibration flow profile and the operating flow profile aredetermined, wherein with these ratios, the current measured velocitiesalong the measuring paths are corrected, and wherein that with thiscorrection, the measured velocities are also corrected with the ratiosof the rates of flow when the calibration flow profiles are recorded andwhen the reference flow profiles are recorded, preferably wherein thecorrection factors between the rates of flow set during the recording ofthe calibration flow profile and the operating flow profile aredetermined using interpolation.
 39. The method according to claim 37,wherein especially for Reynolds' numbers smaller than 100,000, thecalibration profiles are measured and stored in dimensionless less formfor a large number of Reynolds' numbers, wherein the current measuredvelocities and the current rate of flow for a dimensionless current flowprofile are processed, and wherein the dimensionless current flowprofile is compared with the calibration flow profiles and corrected byusing said comparison.
 40. The method according to claim 39 wherein:theReynolds' number in zero approximation is determined from the currentflow profile; the average velocity is determined from the flow profilestored for the Reynolds' number in zero approximation; the averagevelocity from the memory is compared with the current average velocity,if there is a deviation between the average velocities above apredetermined limit, a new current average velocity is assumed thatdeviates less from the average velocity from the memory; the Reynolds'number is determined in first approximation from the new currentlydetermined velocity; the average velocity is determined again from theflow profile stored with the Reynolds' number in first approximation,and if there is a new deviation above the predetermined limit, a newcurrent average velocity is again taken that deviates less from theaverage velocity from the memory; and otherwise, the last value for theReynolds' number is used for further processing.
 41. An ultrasoundmethod of measuring the rate of flow of a flowing medium, using ameasuring tube and at least two pairs of ultrasound transducers arrangedon the measuring tube forming a measuring path, in which the rate offlow of the flowing medium is determined from the velocities of themedium along at least two measuring paths, wherein the Reynolds' numberof the flowing medium is measured continuously and the value for therate of flow is corrected using the value for the Reynolds' number,wherein the viscosity of the medium is determined using the rate offlow, the diameter of the measuring tube and the Reynolds number.
 42. Anultrasound method of measuring the rate of flow of a flowing medium,using a measuring tube and at least two pairs of ultrasound transducersarranged on the measuring tube forming a measuring path, in which therate of flow of the flowing medium is determined from the velocities ofthe medium along at least two measuring paths, wherein the Reynolds'number of the flowing medium is measured continuously and the value forthe rate of flow is corrected using the value for the Reynolds' number,wherein the viscosity of the medium is determined using the rate offlow, the diameter of the measuring tube and the Reynolds' number, andwherein the medium is identified using the viscosity and particularlyother medium-dependent measured variables.
 43. The method according toclaim 42, wherein the ultrasound velocity and/or the ultrasound dampingof the medium is determined as another medium dependent measuredvariable.
 44. The method according to claim 41 or 42, wherein the rateof flow is corrected using the value for the Reynolds' number and anerror curve based on empirical data.
 45. The method according to claim44, wherein the Reynolds' number is determined using the velocities ofthe medium along at least two measuring paths.
 46. The method accordingto claim 45, wherein the Reynolds' number is determined using anarithmetical algorithm from the velocities of the medium along differentmeasuring paths.
 47. The method according to claim 46, wherein theReynolds' number is determined based on ratios of said velocities alongdifferent measuring paths.
 48. The method according to claim 46, whereinthe Reynolds' number is determined based on subtractions of thevelocities along different measuring paths.
 49. A device for using theultrasound method of measuring the rate of flow for a flowing medium,the method using a measuring tube and at least two pairs of ultrasoundtransducers arranged on the measuring tube forming a measuring path, inwhich the rate of flow of the flowing medium is determined from thevelocities of the medium along at least two measuring paths, wherein theReynolds' number of the flowing medium is measured continuously and thevalue for the rate of flow is corrected using the value for theReynolds' number, the device comprising a measuring tube, at least twopairs of ultrasound transducers arranged on the measuring tube andforming a measuring path, a transducer that determines the velocities ofthe medium along the measuring paths from the signals of the pair ofultrasound transducers, and an adder that determines the rate of flow ofthe medium from the velocities of the medium along the measuring paths,wherein the device comprises a Reynolds' number meter continuouslyfinding the Reynolds' number and a flow corrector connected to theReynolds' number meter and the adder, wherein there are a profilecorrector and a profile meter one after the other between the transducerand the adder, and wherein the profile corrector has a switch at theinput, an operating flow profile memory connected behind the switch, aflow profile compare connected behind the operating flow profile memory,a profile transducer at the output, and a calibration flow profilememory connected with its input behind an output of the switch and itsoutput in front of one input of the flow profile compare, whereinanother output of the flow profile compare is connected to another inputof the switch, and wherein if the calibration flow profile and theoperating flow profile are not identical, the switch, the operating flowprofile memory and the flow profile compare form a feedback loop. 50.The device according to claim 49, wherein the Reynolds' number meterincludes a turbulent-laminar switch and, connected in parallel to theturbulent-laminar switch, a laminar flow meter, a turbulent flow meter,a transitional flow meter, and an output operation amplifier connectedwith the output of the laminar-flow meter, the turbulent-flow meter andthe transition-flow meter.
 51. The device according to claim 49, whereinit has a viscosity meter connected to the output of Reynolds' numbermeter and the output of the flow corrector.
 52. The device according toclaim 51, characterized by the fact that a medium identifier connectedto the output of the viscosity meter and to at least one input withoutputs of the transducer is provided for identifying the type of mediumby comparing the viscosity and the ultrasound velocity and/or theultrasound damping with stored values, and the transducer determines theultrasound velocity or the ultrasound damping.
 53. A device for usingthe ultrasound method of measuring the rate of flow for a flowingmedium, the method using a measuring tube and at least two pairs ofultrasound transducers arranged on the measuring tube forming ameasuring path, in which the rate of flow of the flowing medium isdetermined from the velocities of the medium along at least twomeasuring paths, wherein the Reynolds' number of the flowing medium ismeasured continuously and the value for the rate of flow is correctedusing the value for the Reynolds' number, the device comprising ameasuring tube, at least two pairs of ultrasound transducers arranged onthe measuring tube and forming a measuring path, a transducer thatdetermines the velocities of the medium along the measuring paths fromthe signals of the pair of ultrasound transducers, and an adder thatdetermines the rate of flow of the medium from the velocities of themedium along the measuring paths, wherein the device comprises aReynolds' number meter continuously finding the Reynolds' number and aflow corrector connected to the Reynolds' number meter and the adder,wherein the Reynolds' number meter includes a turbulent-laminar switch,connected in parallel to the turbulent-laminar switch, a laminar flowmeter, a turbulent flow meter, a transitional flow meter, and an outputoperation amplifier connected with the output of the laminar-flow meter,the turbulent-flow meter and the transition-flow meter.
 54. The deviceaccording to claim 53, wherein it has a viscosity meter connected to theoutput of Reynolds' number meter and the output of the flow corrector.55. The device according to claim 54, wherein a medium identifierconnected to the output of the viscosity meter and to at least one inputwith outputs of the transducer is provided for identifying the type ofmedium by comparing the viscosity and the ultrasound velocity and/or theultrasound damping with stored values, and the transducer determines theultrasound velocity or the ultrasound damping.